1. Field of the Invention
The present invention relates to a small viscous precision damper wherein the cap is attached by a tongue and groove joint which is ultrasonically welded.
2. Description of the Prior Art
Viscous dampers are known in the prior art. However, typically the cap includes a cylindrical rim which is inserted over the body of the damper and fastened thereto so as to create a shear connection between the cap and the body. However, such a design, particularly as smaller and smaller dampers are desired to be manufactured, can result in degraded repeatability in manufacturing, sealing and torque aspects. More specifically, some prior art damper designs result in both weld and torque variations due to the outward pressure applied to the cap during welding. This outward pressure decreases the weld penetration and varies the overall height of the damper which creates variations in the damper torque and may further result in silicone leakage. Similarly, some prior art damper designs have decreased weld encapsulation which decreases weld strength and sealing and creates undesired minute strings of plastic which affect customer applications.
An example of a prior art damper using a snap-together design is disclosed in U.S. Pat. No. 4,614,004 entitled "Oil Filled Rotary Damper Having a Symmetrically Shaped Flexible Membrane" issued on Sep. 30, 1986 to Oshida.